Kenneth Suslick of the University of Illinois pioneered research into sonochemistry, a technique that uses the energy of sound to produce cavitation bubbles in a solvent. The bubbles collapse during the compression portion of the acoustic cycle with extreme microscale energy release evidenced by high (microscale) localized temperatures and pressures, estimated at least about 5200.degree. F. and 1800 atm, respectively. Suslick determined that sonochemistry was a way to produce amorphous metal because it provided an adequately rapid quenching of the metal from the melt, and he developed laboratory processes for making amorphous iron agglomerates desired as catalysts in hydrocarbon reforming, carbon monoxide hydrogenation, and other reactions.
Suslick also discovered that he could produce metal colloids if he sonicated the metal precursors (principally volatile metal carbonyls or other organometallics) in a polymeric ligand like polyvinylpyrrolidone or could produce nanostructured supported catalysts if sonication occurred in the presence of suspended inorganic oxide supports, such as silica or alumina.
Suslick's work has focused on catalysts which function through surface phenomena. He has not been as concerned with producing magnetic nanophase particles which have potential for significant improvements in the manufacture of magnetic recording media, permanent magnets, and other coatings and applications provided that the individual particles can be isolated from each other. The nanoparticles that Suslick produced agglomerate readily.
Suslick's work is described in the following articles that we incorporate by reference:
K. Suslick, "Sonochemistry," 247 Science 1439-1445 (23 Mar. 1990); PA0 K. Suslick et al., "Sonochemical Synthesis of Amorphous Iron", 353 Nature 414-416 (3 Oct. 1991); and PA0 K. Suslick, "The Chemistry of Ultrasound," Yearbook of Science & the Future, Encyclopedia Britannica. Inc., 138-155 (1994). PA0 L. Crum, "Sonoluminescence," Physics Today, Sept. 1994, pp. 22-29, and PA0 L. Crum "Sonoluminescence, Sonochemistry, and Sonophysics", J. Acoust. Soc. Am. 95(1), Jan 1994, pp. 559-562.
Similar work is described in the following articles by Lawrence Crum, that we incorporate by reference:
Gibson discussed anisometric cobalt nanoclusters in his recent article in Science (vol. 267; March 3, 1995), where he produced anisometric (hexagonal disk-shaped) cobalt nanoclusters about 10) nanometers in width and 15 nanometers in thickness with oriented (001) crystals comparable to cells of .alpha.-cobalt. Gibson sonicated Co.sup.2+ (aq) with hydrazine to produce the nanoclusters that were small enough to be strongly influenced by Brownian forces and thereby resistant to agglomeration. Working with hydrazine, however, on a commercial scale poses considerable safety questions.